1. Field of the Invention
The present invention is related to an improved spring hinge, and more particularly to the improved structure of a shaft and holding heads of such a spring hinge.
2. Description of Related Art
A mounted spring hinge can make an opened door close again automatically. As shown in FIG. 1, generally, the spring hinge includes a first member 10, a second member 20, a spring 30, a spring seat 40, a tensile adjustment seat 50, a tensile adjustment pin 60, shaft 70 and two holding heads 80, 81.
One side of the first member 10 is curved to form a tubular portion 11 while the other flat plate portion is provided with securing holes 12 for mounting the hinge on a door or door frame. The spring seat 40 has a central hole 41 providing for the penetration of shaft 70. On the edge of the hole 41 a gap 42 is provided for embedding one end 31 of spring 30 in position within the spring seat 40. Besides, this spring seat 40 is secured at the bottom of the tubular portion 11 of the first member by screwing or riveting. As shown in FIG. 3, the gap 42 of spring seat 40 is embedded and blocked against a concave part 13 provided at the bottom end of the tubular portion 11. The bottom end 31 of spring 30 can be connected to the first member 10 by means of the spring seat 40 indirectly.
The bottom of the tensile adjustment seat 50 can be inserted into the top end of the tubular portion 11 of the first member 10 and is provided with an aperture 52 for the insertion of the top end 32 of spring 30 therein. The second member 20 includes a plate portion 21 and two connecting pieces 23, 24 located at the top and bottom ends of one side respectively. Securing holes 22 are provided on the plate portion 21 for mounting the member 20 on doors or door frames, and each connecting piece 23, 24 includes a hole 25, 26 formed therein, respectively.
The two connecting pieces 23 and 24 are pressed into the spring seat 40 and tensile adjustment seat 50 respectively and hold the first member 10 and second member 20 together to form a hinge by means of the penetration of the shaft 70 between them. Besides, a pressing spring can be maintained between the first member 10 and second member 20 by inserting the tensile adjustment pin 60 into one of the suitable adjustment holes 53 located on the tensile adjustment seat 50.
It should be noted that the other side of the first member 10 can also be curved to form another tubular portion for connecting with a third member which is the same as the second member 20 in order to provide a double spring hinge.
The present invention particularly concerns the improvement of the shaft 70 and holding heads 80, 81. With reference to FIG. 1, it should be understood that the holding heads 80, 81 are screwed to the top and bottom ends of the shaft 70 respectively in order to prevent the dropping out of the shaft 70. Since the spring hinge includes a strong spring inside, if the holding head is loosened so that the shaft 70 drops out, the whole hinge will shoot out from the tubular portion because of the elastic force of the spring inside. This is dangerous because it may cause doors or windows to tilt over or fall off which may cause injury to people nearby.
The holding heads of known spring hinges, such as shown in FIG. 1, are made of metal or plastic with internal thread which can be engaged with the external thread of the shaft 70. But, this type of connection between the holding heads 80, 81 and shaft 70 has the disadvantage of being loose and falling off easily and frequently. Both providing a fixed hole and pin between the holding head and shaft, and riveting the holding head and penetrated shaft together are possible methods to overcome the drawbacks described above, but such methods may damage the outward appearance of the holding head and it is difficult to increase the production speed because of its complicated manufacturing process.